The expression $1.08s + 1.02b$ predicts the end-of-year value of a financial portfolio where $s$ is the value of stocks and $b$ is the value of bonds in the portfolio at the beginning of the year. What is the predicted end-of-year value of a portfolio that begins the year with $\$200$ in stocks and $\$100$ in bonds? $\$$
Answer: Beginning the year with $\${200}$ in stocks and $\${100}$ in bonds tells us that $s={200}$ and $b={100}$. Let's substitute $s={200}$ and $b={100}$ into the expression and evaluate: $\begin{aligned} &\phantom{=}1.08s + 1.02b\\\\ &= 1.08({200})+1.02({100})\\\\ &= 216+102\\\\ &={318} \end{aligned}$ A financial portfolio that begins the year with $\${200}$ in stocks and $\${100}$ in bonds is predicted to be valued at $\${318}$ at the end of the year.